a m6 bolt with a m5 washer??
(Note, I'm an accountant, not a techie....)
I measured the pressure plate hole that accommodate the springs:
21mm
The M5/M6 Probolt washers have a 19mm OD, leave 1mm "room" on either side
The original bolts have a 16.7 mm washer, which has a little lateral play, so in effect has 2mm "room" on either side.
I will let the technie's chip in to say if this is of concern or not.
If not, what is the view on using the aluminum (comes in color) bolts? Too weak must use stainless?
the holes themselves are 61mm "deep"
But there is "only" 33mm thread; so no worries if bolts are a bit longer
(I put in a M6 bolt with 40mm thread length and it "stopped" with 7mm to go)